This book is the product of my PhD research at University College London. I am grateful to the many people and organisations that have made my research both possible and enjoyable. I have benefited greatly from the companionship and support of all of my colleagues in the Computer Science and Anatomy departments during the course of this work. The following paragraphs can only recognise some of the more direct contributions.

Many thanks are due to Michael Recce for his enthusiastic and constructive supervision. Michael has been generous with his time, his ideas, and his lab space. I am also indebted to Michael for his careful reading of draft versions of this document and his valuable suggestions about its style and content.

Jim Donnett has made many much-appreciated contributions to this work, ranging from hardware design and debugging through to a detailed reading of the thesis. Jim's breadth and depth of knowledge have been invaluable, and his friendship and sense of humour have helped me through some trying moments.

I owe a great deal to Clive Parker for the construction of my robot, ARNE. Thanks to Clive's electronic and mechanical skills, a loose collection of components was transformed into an effective research tool.

David Brown of the Statistics Department kindly took the time to advise me about the statistical analysis of my results, despite having been ‘Volunteered’ for the job. His insight and suggestions were most welcome.